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PICCINELLI, ELSA. « Environmental impact of industrial plants combustion processes : kinetic and formation/destruction mechanisms of PolichlorinatedDibenzo-p-Dioxins and PolichlorinatedDibenzoFurans ». Doctoral thesis, Università degli Studi di Milano-Bicocca, 2009. http://hdl.handle.net/10281/10060.
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The aim of the project was to study the mechanism of formation and degradation of PolyChlorinatedDibenzo-p-Dioxins (PCDDs) and PolyChlorinatedDibenzoFurans (PCDFs) in combustion processes. Today the challenge is to demonstrate that the conclusion based on laboratory scale experiments and the models coming from the results are useful tools to estimate emissions and to prevent or reduce PCDD/F (sum of PCDDs and PCDFs) formation in the flue gas cleaning system of plants. Following this, the study was developed at two different scales:
Laboratory scale. The native carbon oxidation and PCDD/F formation were simultaneously studied at different temperatures (230-350 °C) and times (0-1440 min) in order to establish a direct correlation between the disappearance of the reagents and the formation of the products. The kinetic runs were conducted in a experimental set up where conditions were chosen to gain information on the role of fly ash deposits in cold zone of the plant in PCCD/F formation reaction
Real plant scale. An extensive experimental study of a secondary aluminium casting plant flue gas cleaning system was performed. In particular, on the strength of the knowledge obtained by laboratory studies and the results of the samplings, the best strategies to prevent PCDD/F formation were identify and Air Pollution Control Device (APCD) performance was improved.
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Bhattacharjee, Linkon. « DEGRADATION OF 1,4-DIOXANE USING METALLIC NANOPARTICLES UNDER VISIBLE LIGHT ». OpenSIUC, 2020. https://opensiuc.lib.siu.edu/theses/2655.
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1,4-dioxane is an emerging contaminant and fully miscible organic compound which has been found extensively in wastewater effluent. Conventional water treatment technologies like carbon adsorption, and air stripping are inefficient in removing this extremely mobile and persistent contaminant from water. In this study, different types of metallic nanoparticles, e.g., nanoscale zero-valent iron (nZVI), γFe2O3, and Fe(III)-doped TiO2 were used to investigate the removal of 1,4-dioxane under visible light. These nanoparticles were characterized with scanning electron microscope (SEM), transmission electron microscope (TEM) and dynamic light scattering (DLS). The experiments were first carried out using deionized water (DIW) at pH 7 and pH 3. nZVI was found more efficient than other nanoparticles under visible light irradiation at pH 3. No 1,4-dioxane removal was obtained for all cases at pH 7 under visible light, or at pH 3 in dark. Moreover, light intensity also plays a significant role in 1,4-dioxane removal. Removal of 22.3%, 40.0% and >99.9% of 1.4-dioxane was reached under 2.4 mW/cm2, 2.6 mw/cm2 and 3.25 mW/cm2 light intensities, respectively, after 6 h of irradiation. The most efficient nanoparticle nZVI was applied to wastewater effluent from Carbondale Southeast Wastewater Treatment Plant. From the results, it was found that 1,4-dioxane degradation took longer time in wastewater effluent than in DIW, because of the presence of other constituents in the wastewater sample. nZVI is also capable of removing 1,4-dioxane in presence of trichloroethylene (TCE) and tetrachloroethylene (PCE) at pH 3 under visible light. In comparison, TiO2 nanoparticle is capable of degrading 1,4-dioxane under visible light or under sunlight at pH 7. Moreover, TiO2 removed 1,4-dioxane in presence of both TCE and PCE at pH 7 under visible light or sunlight. This study found a cost-effective and efficient solution for removing 1,4-dioxane from wastewater effluent that can be reused, by using metallic nanoparticles under visible light.
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Manthey, Jacek Tadeusz. « Degradation of thin silicon dioxide films and EEPROM cells / ». [S.l.] : [s.n.], 1990. http://library.epfl.ch/theses/?nr=832.
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Namor, Omar G. « Sorbic acid interaction with sulphur dioxide in model food systems ». Thesis, University of Surrey, 1987. http://epubs.surrey.ac.uk/847780/.
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Sorbic acid and sulphur dioxide are often used together, as preservatives,in many foods. Sorbic acid is known to undergo degradation in aqueous solutions, and this degradation appears to be accelerated in the presence of sulphur dioxide. The interaction between sorbic acid and sulphur dioxide is the subject of this thesis. The work is subdivided into five chapters, as follows: The first chapter deals with the chemistry of sorbic acid acid and sulphur dioxide. The second chapter describes a study of the degradation products of sorbic acid, in aqueous systems, in the presence of sulphur dioxide and a possible mechanism for the occurrence of these products is proposed. Chapter three deals with the preparation and degradation of 6-[[13]C] sorbic acid in order to find evidence for, or against, the mechanism proposed in chapter two. It also gives details of syntheses attempted in order to obtain 6-[[13]C] sorbic acid. The interaction of sorbic acid and sulphur dioxide in real food systems is the subject of the fourth chapter. The food systems studied were mayonnaise, tomato puree, orange juice and cottage cheese. The effect of packaging on the rate of degradation of sorbic acid was also investigated. The final chapter deals with a microbiological study of two homologues of sorbic acid, 2,4-heptadienoic acid, 2,4-octadienoic acid. The fungicidal activity of these two compounds, towards selected fungi, was analysed. 4-0xobut-2-enoic acid, a degradation product of sorbic acid in aqueous systems, was also analysed as a possible fungistat.
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Kamwilaisak, Khanita. « The combination of laccase and titanium dioxide for lignin degradation ». Thesis, University of Sheffield, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.521978.
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Harris, Neil. « The degradation of lubricant and fuel due to nitrogen dioxide ». Thesis, University of York, 2016. http://etheses.whiterose.ac.uk/20881/.
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Due to the recent trends to improve fuel economy and reduce emissions there have been changes to engine design, resulting in higher temperatures and more nitrogen dioxide in the engine, as well as increased biodiesel usage. Overall, this has led to a more severe environment for the engine lubricant, increasing degradation; an understanding of the mechanism is required to prevent this degradation. Squalane has been used as a model base oil and degraded in an environment of nitrogen dioxide at 150 oC. GC x GC has been used to separate the resultant product mixture, and time of flight mass spectrometry identified products as the squalane alcohol, ketones and alkane fragments. Nitrogen containing products have been identified using a GC x GC with nitrogen chemiluminescence detector, the highest concentration of product has been identified as nitromethane. Other nitroalkanes have been proposed based on retention index. The experiments have been repeated for mixtures of nitrogen dioxide and oxygen and no unique products have been identified. The impact of biodiesel degradation has been assessed using methyl linolate as a model compound and applying the same techniques as used for the base oil model system. The products have been identified as being due to fragmentation of the methyl linolate and the formation of ketones. The largest nitrogen containing product concentration being the nitromethane, other nitoalkanes which have been identified. This experimental evidence has led to the elucidation of the mechanism for nitration which is presented and compared with the autoxidation mechanism. The nitration is hydrogen abstraction initiated by NO2. The second stage is the addition of NO2 to form an alkyl nitrite. The CO-NO bond is comparable to a peroxide, therefore decays to an alkoxy radical. The alkoxy radical can then follow the established mechanisms in autoxidation to form the observed products.
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Stewart, Laine Kincaid. « Tungsten trioxide and titanium dioxide photocatalytic degradations of quinoline ». [Ames, Iowa : Iowa State University], 2009.
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Hathway, Timothy Lee. « Titanium dioxide particle size effects on the degradation of organic molecules ». [Ames, Iowa : Iowa State University], 2007.
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Searle, J. R. « Titanium dioxide pigment photocatalysed degradation of PVC and plasticised PVC coatings ». Thesis, Swansea University, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.638788.
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Due to its ubiquitous presence in paints of all colours, titanium dioxide represents the primary pigment used in Organically Coated Steel (OCS) for construction applications. However the semi-conducting nature of TiO2 translates into a possibility of inducing photodegradation when exposed to Ultra Violet (UV) radiation such as that present in sunlight. Initial research concentrated on developing a test procedure of the photoactivity of these pigments within a PVC binder. Model coatings, using pigments of known performance, have been tested to evaluate the success of this rapid test technique and excellent correlation has been shown. Building on this, Chapter 4 details a unique cell that has been designed, constructed and tested resulting in a more versatile testing environment. This cell has been used to examine the photostability of 4 commercially available pigments while present within a standard emulsion paint binder. Chapters 5 and 6 detail work performed on Plasticised PVC paint films and the resultant effects this has on the kinetics of photodegradation as monitored via the evolution of CO2. Also incorporated into this design is the ability to identify and quantify volatile organic components that are evolved during the degradation process, thus providing information regarding the photodegradation mechanism occurring within the film. It has been found that in these model films, the addition of plasticiser increases the rate of photogenerated CO2 and also produces volatile components that can be directly related to the parent plasticiser molecule. There is some evidence to suggest that for certain plasticisers, a sacrificial protection mechanism is at work, resulting in increased CO2 evolution but decreased attack on the binder matrix. Finally in Chapter 7, a number of complimentary techniques are employed to assess the effect that TiO2 photocatalysed PVC degradation has on the underlying substrate material. The techniques include electrochemical impedance spectroscopy (EIS), electro-generated chemiluminescence (ECL) and 3-D scanning vibrating electrode technique (3-D SVET). Photodegradation leads to porosity development in coatings and eventual through coating penetrative defects lead to corrosion.
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Zhang, Geshan. « The Degradation of Cyanotoxins by using Polymorphic Titanium Dioxide Based Catalysts ». University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1406810827.
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Sohn, Yon S. « Photoelectrocatalytic degradation of organic dye molecules on titanium dioxide nanotubular array ». abstract and full text PDF (UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1455707.
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Upadhyaya, Ashraya. « Nitrogen Doped Titanium Dioxide in the Photocatalytic Degradation of Methylene Blue ». ScholarWorks@UNO, 2018. https://scholarworks.uno.edu/honors_theses/120.
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Titanium dioxide(TiO2) is a stable, effective and well-known photocatalyst for degradation of pollutants. However, its practical applications are limited due to the need for energy higher than 3.2 eV, or a wavelength lower than 390 nm (high frequency waves, ultraviolet and above) hindering its ability to effectively work in the visible light region (about 400 nm to 700 nm). Nitrogen-doped TiO2 (N-TiO2) has garnered some attention as a photocatalyst as it appears to work even in the visible light region. This could allow the utilization of a larger part of the solar spectrum. This thesis presents the results of photocatalytic degradation of methylene blue (MB) carried out under simulated visible light by using TiO2 and N-TiO2(doped in the lab) to evaluate and compare their efficiencies under similar conditions.
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DAVYDOV, LEV. « PHOTOCATALYTIC DEGRADATION OF ORGANIC CONTAMINANTS : NOVEL CATALYSTS AND PROCESS ». University of Cincinnati / OhioLINK, 2001. http://rave.ohiolink.edu/etdc/view?acc_num=ucin995381776.
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Witt, Betsy Suzanne. « Bioaugmentation of TreeWells® to Enhance the Aerobic Degradation of 1,4-Dioxane at High Concentrations ». Ohio University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1534768504663964.
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Cruz, Vivian. « Titanium dioxide photocatalytic degradation of aliphatic ethers and their primary oxidation products ». FIU Digital Commons, 2001. http://digitalcommons.fiu.edu/etd/2677.
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Two studies were performed to obtain fundamental mechanistic information on the TiO2 catalyzed degradation of organic substrates irradiated at 350 nm in dilute aqueous solutions under oxygenated conditions: (a) The photodecomposition of methyl tert-butyl ether (MTBE) and its intermediate products from β - oxidation, 2-methoxy-2-methylpropanol and 2-methoxy-2-methylpropanal. (b) The photodecomposition of two haloethers, bis-(2-chloroethyl) ether, and bis-(2-chloroisopropyl) ether. Controls were carried out throughout the two studies in the absence of light, and without the semiconductor in order to evaluate the role of photolysis.
The syntheses of proposed intermediate products, 2-methoxy-2-methylpropanol, 2-methoxy-2-methylpropanal, 2-methoxy-2-methylpropanoic acid, 2-chloroethyl formate, and 1-chloro-2-propyl acetate, were performed. The formation of these products in the titanium dioxide photocatalytic oxidation of the substrates of interest was also confirmed. TiO2 photocatalysis is a very effective method for the mineralization of aliphatic ethers and their primary oxidation products.
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Choi, Wonyong Hoffmann Michael R. « Photooxidative and photoreductive degradation of chlorinated hydrocarbons on aqueous titanium dioxide colloids / ». Diss., Pasadena, Calif. : California Institute of Technology, 1996. http://resolver.caltech.edu/CaltechETD:etd-05052006-084215.
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Yu, Wenbin. « Deterioration of Polyethylene Exposed to Chlorinated Species in Aqueous Phases : Test Methods, Antioxidants Consumption and Polymer Degradation ». Doctoral thesis, KTH, Polymera material, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-116562.
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This thesis presents a study of antioxidant depletion in water containing chlorinated species (water containing 10 ppm either Cl2 or ClO2, buffered to pH = 6.8), the degradation products in the aqueous phase, and polyethylene pipe degradation scenarios. A low molecular weight hydrocarbon analogue (squalane) was used instead of solid polyethylene as the host material for the antioxidants, and the depletion of antioxidants has been studied. The phenolic antioxidant Irganox 1010 was consumed ca. 4 times faster in water containing 10 ppm ClO2 than in water containing 10 ppm Cl2. The different degradation products in extracts from the aqueous phase identified by infrared, liquid chromatography and mass spectrometry revealed the different degradation mechanisms between ClO2 (" cleavage) and Cl2 (hydrogen substitution). The squalane test shows no energy barrier between 30 and 70 °C, and the activation energy of the antioxidant in solid PE was found to be ca. 21 kJ mol-1. A linear relationship has been established between the time to reach antioxidant depletion in the polyethylene tape samples and the time to reach depletion in samples based on squalane containing the same antioxidants. The surface oxidation and surface embrittlement of PE tape on long time exposure have been studied by IR and SEM. Pressure testing on medium density PE pipes with a controlled pH aqueous media (6.8 ± 0.2) containing 4 ppm either ClO2 or at 90 °C showed that the stabilizers were rapidly consumed towards the inner pipe wall and the rate of consumption in ClO2 was 4 times greater than in Cl2 solution. The subsequent polymer degradation was an immediate surface reaction. It was confirmed by differential scanning calorimetry, infrared spectroscopy and size exclusion chromatography that, in the surface layer which came into contact with the oxidizing medium, the amorphous component of the polymer was heavily oxidized leaving a highly crystalline powder with many carboxylic acid chain ends in extended and once-folded chains.QC 20130122
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Coleman, Heather Margaret. « Photocatalysis of oestrogens in water ». Thesis, University of Ulster, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.342532.
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Haddad, Abdelouahab. « The influence of carbon dioxide on the aqueous corrosion of steel ». Thesis, University of Nottingham, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.334971.
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Noganta, Siyasanga. « Photocatalytic degradation of organic pollutants using Ag-Fe₃O₄/SiO₂/TiO₂ nanocomposite ». Thesis, University of the Western Cape, 2015. http://hdl.handle.net/11394/5208.
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>Magister Scientiae - MScThe global lack of clean water for human sanitation and other purposes has become an emerging dilemma for human beings. The presence of organic pollutants in wastewater produced by textile industries, leather manufacturing and chemical industries is an alarming matter for a safe environment and human health. For the last decades, conventional methods have been applied for the purification of water but due to industrialization these methods fall short. Advanced oxidation processes and their reliable application in degradation of many contaminants have been reported as a potential method to reduce and/or alleviate this problem. Lately, it has been assumed that incorporation of some metal nanoparticles such as magnetite nanoparticles as photocatalyst for Fenton reaction could improve the degradation efficiency of contaminants. Core/shell nanoparticles, are extensively studied because of their wide applications in the biomedical, drug delivery, electronics fields and water treatment. The current study is centred on the synthesis of silver-doped Fe₃O₄/SiO₂/TiO₂ photocatalyst. Magnetically separable Fe₃O₄/SiO₂/TiO₂ composite with core–shell structure were synthesized by the deposition of uniform anatase TiO₂ NPs on Fe₃O₄/SiO₂ by using titanium butoxide (TBOT) as titanium source. Then, the silver is doped on TiO₂ layer by hydrothermal method. Integration of magnetic nanoparticles was suggested to avoid the post separation difficulties associated with the powder form of the TiO₂ catalyst, increase of the surface area and adsorption properties. Lastly and most importantly magnetic nanoparticles upsurge the production of hydroxyl groups or reduced charge recombination. The a synthesized catalysts were characterized using Transmission Electron Microscopy, X-ray Diffraction; Infra-red Spectroscopy, Scanning Electron Microscope and Energy Dispersive Spectroscopy. Other characterization techniques includeVibrating Sample Magnetometry, Brunauer Emmett Teller analysis and Thermogravimetric analysis. The average size of the particles size is 72 nm. Furthermore the photocatalytic performances of the magnetic catalysts were assessed in comparison with that commercial titanium dioxide for the degradation of methylene blue using photochemical reactor under ultra violet light. The results showed that the photocatalytic activity was enhanced using Fe₃O₄/SiO₂/TiO₂ and Ag-Fe₃O₄/SiO₂/TiO₂ compared with that for Fe₃O₄, commercial titanium dioxide powder.
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Li, Haitao. « Synthesis of Titanium Dioxide Photocatalyst with the Aid of Supercritical Fluids ». Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4912.
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Titanium Dioxide (TiO2) emerged as one of the most popular photocatalysts since 1970's. However, its photocatalytic activity requires UV irradiation due to its large band gap unless further functionalization or modifications are performed. Furthermore, recovery issue has always been a major drawback, if the more effective form nano particles are utilized.
The key objectives of this research were synthesizing new TiO2 based photocatalyst systems that are effective with both the UV and the visible light while utilizing novel superior environmentally friendly techniques enabling development of nano-structured photocatalysts that can be easily recovered. In this dissertation research, highly porous nano-structured TiO2/WO3/Fe3+ aerogel composite photocatalyst are prepared, characterized, and tested for model photocatalytic reactions. The photocatalyst structure is tailored to capture environmental pollutants and enable their decomposition in-situ under both UV and visible light through photodecomposition to smaller benign substances.
A novel and green method is applied to prepare unique surfactant templated aerogel photocatalysts with highly porous nano-structure, high surface area, and tailored pore size distribution. Sol-gel process followed by supercritical fluids extraction and drying allowed synthesis of highly porous composite TiO2/WO3 aerogel. The surfactant template was completely removed with the aid of a supercritical solvent mixture followed with heat treatment. Fe3+ ion was incorporated within the composite aerogel photocatalyst as dopant either at the sol-gel co-precipitation step or at a subsequent supercritical impregnation process. Supercritical drying followed with heat treatment results in titanium dioxide with the most profound anatase crystal structure. Neutral templates were used to further enhance retention and tuning of the nano-pore structure and the surface properties. The Nitrogen adsorption-desorption isotherms methods were used to follow the removal of solvents and templates as well as tracking the textural properties of the synthesized aerogel. Surfactant-templated aerogels, which show remarkable thermal stability and uniform pore size distribution, exhibit specific surface areas three times more than the highly optimized commercial nano-particles, industry standard TiO2 photocatalyst Degussa P-25, even after heat treatment.
The synthesized catalysts were characterized by using SEM, FIB, EDS, XRD, XPS and porosimetry prior to post photocatalytic activity evaluation through a model photocatalytic reaction. The band gaps of the catalysts were also determined by using diffuse reflectance spectroscopy.
The model reaction employed Methylene Blue (MB) photo-oxidation under UV and visible light. Resulting aerogel TiO2/WO3/Fe3+ photocatalyst exhibited comparable photocatalytic capability to Degussa P25 under UV light exposure and offered much superior photocatalytic capability under visible light exposure.
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Benham, T. J. « Some effects of carbon dioxide based atmospheres on the fretting of mild steel ». Thesis, University of Nottingham, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.357758.
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Chau, Robert Shu-Keung. « Charge conduction, trapping and dielectric degradation in stacked silicon nitride-silicon dioxide insulating films / ». The Ohio State University, 1989. http://rave.ohiolink.edu/etdc/view?acc_num=osu148759996359414.
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Alsharari, Reem M. « The Study of Nanoparticle Titanium Dioxide-Based Hydrogel for Dye Adsorption and Photo-Degradation ». DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2019. http://digitalcommons.auctr.edu/cauetds/186.
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The objective of this research was to study the adsorption and photodegradation of crystal violet (CV) dye by using poly(2-hydroxyethylmethacrylate) (PHEMA) hydrogel and nanocomposite TiO2-PHEMA hydrogel. Since the TiO2 nanoparticle has poor solubility, another goal of this study was to make a uniform TiO2 nanocomposite gel. These gels can be used in water treatment and can be easily photodegrade by exposure of sunlight which is similar to exposing to UV-vis. PHEMA was synthesized by free radical polymerization. The nanocomposite gels were characterized by FT-IR and XRD to confirm the presence of TiO2 nanoparticles and CV dye inside the PHEMA hydrogel. The XRD data showed that not only maintaining the crystallinity of the three different phases that had been used, but also the uptake of the dye inside the nanocomposite gels. Moreover, the FT-IR demonstrated the presence of the functional groups of the chemical structure of the gel as well as the nanocomposite gels with the CV dye. The adsorption of CV dye was examined through monitoring UV-Vis absorption. The kinetic study indicated the adsorption of the dye by the nanocomposite gels until reached equilibrium, which is the zero concentration. The photodegradation of CV dye was examined using a medium pressure Hg lamp. It was determined that the composite gels adsorb CV dye from the solution at the beginning while under the photochemical condition. Eventually, the dye in the gel was photodegraded, indicating that in the gel system, the photodegradation process is still effective to dyes. The composite gels containing pure anatase phase titanium are much better photocatalysts and took less time of adsorption than those containing pure rutile and anatase/rutile mixed phases of titania.
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Ferreira, Iza Natália Moraes. « DEGRADAÇÃO FOTOCATALITICA DE PESTICIDAS ORGANOFOSFORADOS MEDIANTE O USO DE TiO₂/UV EM AMBIENTE SATURADO ». Universidade Federal do Maranhão, 2014. http://tedebc.ufma.br:8080/jspui/handle/tede/999.
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Previous issue date: 2014-07-15Pesticides that are used to combat pests in plantations operate in parallel on other species causing serious problems to be toxic and remain in the environment for a long time. This study aimed to evaluate the photocatalytic degradation of an organophosphorus pesticide by advanced oxidation processes, the insecticide methyl parathion were selected (PM), widely used in Brazilian crops, especially Maranhão. The POA consisti the application of immobilized TiO₂ as photocatalyst and UV radiation to accelerate the degradation of the pesticide. Effects of some parameters such as the illumination time and initial concentration of the compounds during photocatalytic degradation were studied. Was optimized a method for pesticide analysis by liquid chromatography and two advanced reviews (POA) for the destruction of this contaminant oxidation processes. The POA tested were: combination TiO₂/UV and TiO₂/H₂O₂/UV. The analytical method was suitable for evaluation of the POA, with limits of detection and quantification limits of 0,05 mg Lˉ¹ and 0,17 mg Lˉ¹, respectively, this method was then applied to monitoring the concentrations of the pesticide during application of POA procedures. Among the POAs, both cases showed good results in catalytic destruction of pesticide, where 100% of the pesticide was removed immediately first 30 min of exposure to UV radiation. The results showed that the efficiency of photodegradation of PM increases with increasing illumination time and photodegradation efficiency decreases with an increase in the initial concentration of PM.
Os pesticidas que são utilizados no combate às pragas em plantações atuam paralelamente sobre outras espécies causando sérios problemas por serem tóxicos e permanecerem no ambiente por um longo tempo. Este trabalho propôs avaliar a degradação fotocatalítica de um pesticida organofosforado por processos oxidativos avançados, tendo sido selecionado o inseticida paration metilico (PM), amplamente utilizado nas lavouras brasileiras, em especial maranhenses. O POA consisti na aplicação do TiO₂ imobilizado, como fotocatalisador, bem como a radiação UV para acelerar o processo de degradação do pesticida. Foram estudados efeitos de alguns parâmetros, tais como o tempo de iluminação e concentração inicial dos compostos durante a degradação fotocatalítica . Foi otimizado um método para análise do pesticida por cromatografia a líquido bem como avaliados dois processos oxidativos avançados (POA) para a destruição deste contaminante. Os POA testados foram os seguintes: combinação TiO₂/UV e TiO₂/H₂O₂/UV. O método analítico mostrou-se adequado para fins de avaliação do POA, com limites de limites de detecção e quantificação de 0,05 mg Lˉ¹ e 0,17 mg Lˉ¹, respectivamente, este método foi, então, aplicado para o monitoramento das concentrações do pesticida, durante a aplicação dos procedimentos POA. Entre os POAs, os dois casos apresentaram bons resultados na destruição catalítica do pesticida, onde 100% do pesticida foi removido logo nos primeiro 30 min de exposição à radiação UV. Os resultados mostraram que a eficiência de fotodegradação do PM aumenta com o aumento do tempo de iluminação e a eficiência de fotodegradação diminui com o aumento na concentração inicial do PM.
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ABU, BAKAR FARIDAH. « Towards new generation of sustainable catalysts:Study of shape and size controlled TiO2 nanoparticlesin photocatalytic degradation of industrial dye ». Thesis, University of Canterbury. DEPARTMENT OF CHEMISTRY, 2014. http://hdl.handle.net/10092/10044.
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Due to industrialization and population growth, environmental contamination caused by organic pollutants is becoming an increasing problem worldwide. Environmental pollution on a global scale, particularly water pollution, has drawn scientists’ attention to the vital need for environmentally clean and friendly chemical processes. The demand for higher quality water has increased due to population growth, more stringent health regulations and economic development. Untreated wastewater contains a variety of organic compounds with variable toxicities as well as carcinogenic and mutagenic properties. Most contaminants in wastewater contain aromatic rings, which are generally resistant to chemicals, photochemicals and biological degradation.These compounds are very persistent in the environment and have a high potential to negatively affect human health and the ecosystem. Therefore, the removal or degradation
of hazardous material and contaminants from wastewater is a significant global challenge.
This thesis reported on the synthesis of titanium dioxide by using a peroxo method. This synthesis was done in the presence of a number of fluoride-containing surfacemodifying agents to determine the effects of these agents on particle growth, shape and crystallinity. Further, studies were carried out to investigate the modification of F-modified TiO2 with the deposition of Au colloids and an Au9 cluster. A different deposition method is employed
in the synthesis of the TiO2-Au materials to gain a catalyst with the highest photocatalytic activity. The performance of the catalyst was further investigated through pre-treatment and post-treatment of the materials. Finally, several of the synthesised materials were trialled as
photocatalysts using industrial dye Reactive Blue 19 (RB19) as an organic pollutant.
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Shaw, Katherine Elizabeth. « Pure and applied studies of titanium dioxide films for the photoelectrochemical degradation of organic effluent ». Thesis, University of Newcastle Upon Tyne, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262990.
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Tipsrisukond, Narin. « Impact of lipid degradation processes, and supercritical carbon dioxide extraction on flavor characteristics of lard / ». free to MU campus, to others for purchase, 2003. http://wwwlib.umi.com/cr/mo/fullcit?p3091972.
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BALASUBRAMANIAN, GANESH. « EVALUATING THE EFFECT OF SELECTED PROCESS PARAMETERS ON THE PHOTOCATALYTIC DEGRADATION OF ORGANIC POLLUTANTS ». University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1012410668.
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Nuramdhani, Ida. « Towards Environmentally Benign Wastewater Treatment - Photocatalytic Study of Degradation of Industrial Dyes ». Thesis, University of Canterbury. Chemistry, 2011. http://hdl.handle.net/10092/6400.
Texte intégralRésumé :
Pollution created by textile dyeing operations attracts significant attention because an effluent containing a complex mixture of coloured and potentially toxic compounds can be released with the discharged water. Developing dyes and dyeing conditions to reduce the amount of residual dye contained in any effluent has been one of many approaches to minimise this environmental impact. However, the presence of coloured discharge cannot be totally eliminated using only this strategy. Thus, development of efficient post-dyeing wastewater treatment methods capable of removing coloured products from the water is of paramount importance.
TiO2-mediated photocatalytic degradation of organic dye molecules via oxidation is the focus of the study reported in this thesis. TiO₂ significantly increases the rate of photodegradation of a wide range of organic dyes under mild operating conditions, and is able to mineralise a wide spectrum of organic contaminants. TiO₂ is also one of the very few substances appropriate for the industrial applications.
One of primary aims of this thesis is to test the hypothesis that augmenting standard TiO₂ photocatalysts with Au nanoparticles could increase performance of a catalyst, while immobilizing TiO₂ on SiO₂ support may improve the cost of the process efficiency, i.e. more photocatalytic degradation per particle of TiO₂. Combining TiO₂ doped with gold nanoparticles on SiO₂ support has the potential to provide the highest photocatalytic ability at the lowest cost.
The first half of the thesis is concerned with establishing and optimizing experimental conditions for monitoring photodegradation via UV-Visible spectroscopy. Effects of various conditions such as temperature, sequence of addition of reagents, exposure to light vs. experiments in dark, sampling methods, and the use of quenching agent were examined.
The main conclusions from this study are that light-induced photodegradation using titanium dioxide nanoparticles catalysts is comparatively more efficient than purely chemical catalytic (e.g. non-light mediated) degradation, even if the latter is performed at elevated temperature. Further, the rate of dye degradation is affected considerably by the parameters of the system.
The degradation rate depends strongly on the pH of the solution, due to charges on both the catalyst surface and in the dye. In general, at pH ≤ 6.8, which is the zero charge point for TiO₂, reactions proceeded faster than those at higher pH. Six dyes from four different classes of dyes used in industry were used in this study, and all showed different photodegradation behaviour.
The second half of thesis tests the photocatalytic abilities of various TiO₂-based catalysts: pure TiO₂ (commercial and custom-made in our laboratory), TiO₂-supported gold nanoparticles (Au/TiO₂), SiO₂-supported TiO₂ (TiO₂/SiO₂), and SiO₂-supported Au/TiO₂. The best photocatalytic performance was observed for the custom-made TiO₂ code-named as e-TiO₂, which was synthesized using the sol-gel method in dry ethanol. TiO₂-supported Au55 nanoparticles showed a similar level of catalytic ability but are significantly more expensive. It was observed that dye adsorption played a significant role in the case of SiO₂-immobilized photocatalysts.
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Karmore, Vishal K. « Kinetics Of Polymerization And Degradation By Non-Conventional Techniques ». Thesis, Indian Institute of Science, 2001. http://hdl.handle.net/2005/269.
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Non-conventional techniques for polymerization and depolymerization were investigated. The rates of polymerization were enhanced higher in ultrasonic, supercritical fluids and microwaves. However in these system under certain conditions, simultaneous degradation also occurred. Depolymerization was studied by various methods like thermal degradation in supercritical fluids and in presence of oxidizers, Lewis acid and other organic acids. Degradation by ultrasound and thermal degradation of polymer mixtures were also investigated. The scission of the polymer backbone is random for thermal degradation while the scission occurs at the midpoint for ultrasonic degradation. The degradation rates in all the investigated techniques were higher than the degradation rates observed for pyrolysis. Degradation was possible at low temperature (< 50°C) for oxidative and ultrasound degradation while the degradation rates were two orders of magnitude higher in supercritical conditions. The molecular weight distribution was obtained by GPC analysis and the continuous distribution models were used to obtain the rate coefficients. The activation energies were calculated from the temperature dependence of the rate coefficients.
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Abraham, Berhane Teclesenbet. « Degradation and recovery of polydimethylsiloxane (PDMS) based composites used as high voltage insulators ». Thesis, Stellenbosch : Stellenbosch University, 2004. http://hdl.handle.net/10019.1/49902.
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Thesis (MSc)--Stellenbosch University, 2004.ENGLISH ABSTRACT: Polydimethylsiloxane (PDMS) compounds are utilized in outdoor high voltage insulation due to their low weight, vandalism resistance, better anti-contamination performance and their superior hydrophobic nature. Under severe environmental conditions and over prolonged service time, however, the hydrophobic surface can gradually become hydrophilic and then recover with adequate resting period. In this study, room temperature vulcanized (RTV) PDMS samples were prepared with different formulations and then exposed to corona discharge to evaluate its effect. The influence of different additives, such as different types and amount of fillers and additionally added low molar mass silicone oils, on the hydrophobicity recovery of the material was investigated. The effects of two types of corona treatment were also evaluated. Hydrophobicity recovery of corona and UV-C aged PDMS samples was evaluated by means of static contact angle measurements. Positron annihilation spectroscopy (PAS) gave important information on the micro structural change after corona treatment of RTV PDMS as well as naturally aged high temperature vulcanized (HTV) PDMS samples. The different formulations of the RTV PDMS samples and the effect of the additives were studied with this technique. The formation of a thin, highly crosslinked inorganic silica-like (SiOx) layer was confirmed even at the early stage of degradation. It was also possible to estimate the thickness of the silica-like layer formed during corona exposure that is responsible for the loss and recovery of hydrophobicity. The surface hardness and hydrophilicity change of PDMS samples due to corona treatment were studied simultaneously with force distance measurements by atomic force microscopy (AFM). The adhesive force calculated from the pull-off force-distance curves showed that the adhesive force between the probe and the sample decreased with increasing corona treatment time, indicating hydrophobicity recovery. In addition to this, the increase in hardness after corona exposure provides indirect evidence of the formation of a silica-like layer. In all cases the hydrophilicity and the surface hardness of the PDMS samples increased directly after corona treatment and recovered with time. Two types of FTIR spectroscopy were used to analyse the surface of the polymer.
AFRIKAANSE OPSOMMINGS: Polidimetielsiloksaan (PDMS) word in buitelug hoogspanninginsulasie gebruik as gevolg van sy lae massa, weerstand teen vandalisme, verbeterde anti-kontaminasie werkverrigting en superieure hidrofobiese karakter. Die hidrofobiese oppervlakte kan egter gelydelik hidrofillies word onder uiterste omgewingsomstandighede en oor langdurige dienstyd. PDMS materiaal herstel egter nadat dit genoeg rustyd toegelaat is. Kamertemperatuur-gevulkaniseerde (KTV) PDMS met verskillende formulasies is in hierdie studie voorberei, aan korona ontlading blootgestel, geëvalueer en vergelyk. Die invloed van bymiddels soos verskillende tipes en hoeveelhede vuiler, asook addisionele lae molekulêre massa silikoonolie, op die herstel van hidrofobisiteit van die materiaal is ondersoek. Twee verskillende metodes van korona behandeling is ook geëvalueer. Die herstel van hidrofobisiteit van korona en UV-C verouderde PDMS monsters is met statiese kontakhoekmeting geëvalueer. Positronvernietigingspektroskopie (PVS) is 'n kragtige tegniek wat belangrike inligting oor die mikrostrukturele verandering van korona behandelde van KTV PDMS sowel as natuurlik-verouderde hoë temperatuur gevulkaniseerde (HTV) PDMS monsters gee. Die verskillende formulasies van die KTV PDMS monsters, sowel as die effek van die vullers, is met behulp van hierdie tegniek ondersoek. Die vorming van 'n dun, hoogskruisgebinde, anorganiese silika-agtige (SiOx) laag op die PDMS oppervlak, selfs tydens die vroeë stadium van degradasie, is bevestig. Dit was ook moontlik om die dikte van die silika-agtige laag wat gedurende die korona blootstelling gevorm het, en wat verantwoordelik is vir die verlies aan hidrofobisiteit, te bepaal. Die oppervlakhardheid en hidrofilisiteit verandering van PDMS monsters as gevolg van korona behandeling, was gelyktydig met krag-afstand metings deur middel van atoomkragmikroskopie (AKM) bestudeer. Die kleefkrag, soos bereken van aftrek kragafstandkurwes, dui daarop dat kleefkragte tussen die taster en die monster afneem met toenemende korona behandelingstyd, wat beduidend is op die herstel van hidrofobisiteit. Daarbenewens is die toename van oppervlakhardheid na korona blootstelling "n indirekte bewys van die formasie van 'n silika-agtige laag. In alle gevalle het die hidrofilisiteit en die oppervlakhardheid van die PDMS monsters toegeneem direk na afloop van korona behandeling en gevolglik herstel met tyd. Twee tipes IR spektroskopie metodes is gebruik vir die chemiese-oppervlak analises
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Kataoka, Francini Pizzinato [UNESP]. « Estudo da eficiência fotocatalítica em função da morfologia de nanoestruturas de TiO2 síntetizadas pelo método hidrotérmico ». Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/99660.
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Os problemas ambientais gerados pelo crescimento das atividades humanas e industriais têm aumentado a necessidade pelo desenvolvimento de tecnologias alternativas para a remediação de sistemas aquáticos contaminados. A fotocatálise heterogênea, utilizando dióxido de titânio, tem se mostrado eficiente neste aspecto. Neste trabalho, foram sintetizadas nanoestruturas de TiO2 utilizando como precursor o isopropóxito de titânio pela rota hidrotérmica. Os materiais obtidos foram caracterizados por DRX, FT-Raman, FTIR, BET e MEV. A fim de avaliar a atividade fotocatalítica das amostras produzidas, foram realizados testes de degradação do corante rodomina B sob irradiação UV, luz branca e luz solar. A medida da degradação da molécula foi mensurada por espectroscopia UV-Vis. Os resultados das caracterizações mostraram que a rota de síntese utilizada foi eficiente na produção de nanoestruturas cristalinas de TiO2 com morfologias diferentes e os ensaios de degradação revelaram que a propriedade fotocatalítica dos materiais esta diferente relacionada com a morfologia, a área superficial e a presença de grupos químicos ligados à superfície
The environmental problems generated by tye growth of human and industrial activities have increased the need for the development of alternative technologies for the remediation of contaminated aquatic systems. The heterogeneous photocatalysis using titanium dioxide, has been show effective in this respect. In this work, nanoestructures have been synthesized as a precursor of TiO2 using titanium isopropóxido by the hydrothermal route. The materials were characterized by XRD, FT-Raman, FTIR, BET and SEM. In order to evaluate the photocatalytic activity of the samples produced, tests were performed using degradation of the dye rhodamine B under UV, white light and sunlight. The measurements of the degradation of the molecule was measured by UV-Vis spectroscopy. The results of the characterizations showed that the synthetic route used was efficient in the production of crystalline nanostructured TiO2 with different morphologies and degradation testing revealed that the photocatalytic properties of materials is directly associated to the morphology, surface area and the presence of chemical groups bound to the surface
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Hung, Pao-chen, et 洪保鎮. « Degradation of Gaseous Dioxins with Dielectric Barrier Discharges ». Thesis, 2007. http://ndltd.ncl.edu.tw/handle/70639098823489630987.
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碩士國立中央大學
環境工程研究所
95
The characteristics, formation mechanisms and control technologies of dioxin have been studied for many years. In Taiwan, dioxin content in the ash has been regulated by Taiwan EPA since May 2007. Since activated carbon injection causes the increase of dioxin concentration in the fly ash, it is not regarded as the best available control technology. Dielectric barrier discharge (DBD) has been applied for generating O3 and degrading VOCs and PFCs in flue gas, but has not been investigated for its effectiveness in dioxin removal. This study aims to evaluate the characteristics of PCDD/F removal via DBD at elevated temperature (150oC). DBD reactor is made of the borosilicate glass tube with the inner diameter of 26.8 mm. A stainless steel rod with the diameter of 3.2 mm is used as the inner electrode and the length of discharge region is 105 mm. Experimental tests are conducted at fixed temperature (150oC), space velocity (2000 hr-1), applied voltage (12 kV) and frequency (100 Hz), while the concentrations of oxygen (O2) vary from 0 % to 21% and water vapor [H2O(g)] contents vary from 0 % to 20 %, respectively. The breakdown voltage of the DBD reactor investigated decreases from 12 kV to 8.4 kV as the temperature is increased from 300K to 473K. The maximum applied voltage is greater than 18 kV at 300K and decreases to 8.7 kV as the temperature is increased to 453K. Residual dioxin is less than 2 % of the total injected dioxin at 150oC and system can be operated over 90 minutes with the applied voltage of 12 kV. The mass and TEQ removal efficiencies of dioxin are 61.3 % and 49.9 %, respectively, with pure nitrogen as the carrier gas. As the oxygen content is increased from 5 % to 21 %, the mass removal efficiency is reduced from 44.9 % to 43.1 % and the TEQ removal efficiency decreases from 40.2 % to 36.6 %. The PCDD/Fs removal efficiency does not change significantly with the oxygen content in the gas stream. As the water vapor content is increased from 0 % to 20 %, the highest PCDD/Fs removal efficiency is achieved at 20 % (16.8 % O2) and the mass and TEQ removal efficiencies are 78.1 % and 71.4 %, respectively. On the other hand, the lowest mass removal efficiency (37.3 %) is achieved with the water vapor content of 5 % (20.0 % O2) and the lowest TEQ removal efficiency (32.1 %) is achieved with the water vapor content of 1 % (20.8 % O2). Free radicals including OH can be effectively generated in the DBD reactor if the gas stream contains H2O(g) and O2 as predicted by BOLSIG. On the other hand, free radicals generated from O2 are not effective for PCDD/F removal. Removal of dioxin is mainly achieved by electron collision in the absence of water vapor while OH radical is essential for PCDD/F removal for the gas stream containing H2O(g).
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Tsai, Yu-Ren, et 蔡育仁. « Study on Hazardous Substances from Fly ash ofIncineration by Continuous Degradation of Acid－Dioxins and Lead Metal ». Thesis, 2009. http://ndltd.ncl.edu.tw/handle/tnm249.
Texte intégralRésumé :
碩士國立臺北科技大學
環境工程與管理研究所
97
Fly ash of Incineration treatment by Continuous Degradation of Acid before, if identified it as hazardous industrial waste, as that is a hazardous industrial waste, the disposal and reuse are of limited. If it treatment by Continuous Degradation of Acid after, the fly ash(Reacted Ash)of hazardous will become a harmless substance, so fly ash of Incineration(Reacted Ash) can be reuse it to create a new machine. In this study, in addition to every month for the northern incineration plant analysis fly ash of incineration characteristics in order to assess the condition of the harmless. And at the same time use Continuous Degradation of Acid (Washing of acid method) to laboratory-scale equipment with a variety of experimental conditions (such as the hydraulic retention time, concentration of acid solution, etc.). The strong acid solution resulted in an increase in temperature to overcome fly ash (Reacted Ash) resistance transmission. At the same time it can reduce the heavy metals leaching in fly ash (lead-based) and destruction of dioxin structure, its laws and regulations are in line with standards, and at the same time control the chloride ion content of fly ash to reduce the fly ash (Reacted Ash) of the harmful nature. The experimental results in accordance with the present study analysis, for by the continuous degradation of acid treatment, hazardous substances and chloride ions content in fly ash and their reduce the effectiveness. It can be informed of the following important conclusions: 1. Reacted Ash TCLP Pb value has been continuous degradation of acid will decline significantly, and in accordance with the regulations and standards (5 mg/L). In addition the total contents of lead and TCLP Pb value compared to the leaching rate of lead can be learned by the continuous degradation of acid processing leaching rate of lead is a great fall trend. Indicating continuous degradation of acid processing remove lead heavy metals have good results. 2. Compared to the total content of chlorine by continuous degradation of acid, the water-soluble chloride ions of Reacted Ash to reduce the effectiveness will be higher, at about 72.79% ~ 88.26%, increasing the concentration of acid solution to reduce the effectiveness have better results. 3. When dealing with continuous degradation of acid use the concentration of acid 10.0M nitric acid +11.4M sulfuric acid, solid-liquid ratio 1:10, temperature 25 ℃ and 20 minutes hydraulic retention time, the dioxin content of 0.0956 (ng-I-TEQ/ gdw), dioxin reuse standards in line with the 0.1 (ng-I-TEQ/gdw)), the results showed that continuous degradation of acid for hazardous substances of Fly ash(Reacted Ash) removal dioxin is available and in accordance with the reuse regulations and standards.
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Yang, Tzu-Hsuan, et 楊子萱. « Using Palladium/Graphene Catalyst for Degradation of Persistent Organic Pollutants in Organic Solvents-Dioxins and Polybrominated Diphenyl Ethers ». Thesis, 2018. http://ndltd.ncl.edu.tw/handle/f35neg.
Texte intégralRésumé :
碩士中原大學
化學研究所
106
In this study, a new type of low-temperature catalyst was synthesized. Palladium metal was embedded onto the surface of graphene to prepare a Palladium/Graphene (Pd/G) catalyst. Degradation of dibenzo-p-dioxin (DD), 2-chlorodibenzo-p-dioxin (2CDD), Dibenzofuran (DBF) and 4-Bromodiphenyl ether (4-BDPE) in organic solvents was achieved by using this Pd/G catalyst with the presence of hydrogen gas. The optimal rate of degradation was studied by UV/VIS spectrometry. The experimental results show that by 20 mg of Pd/G catalyst is optimal for the degradation of DD, 2CDD, and 4-BDPE at 115 °C and 20 bar of hydrogen pressure for 1 hour. Whereas for DBF, 20 mg of Pd/G catalyst at 95 °C and 20 bar of hydrogen pressure for 30 minutes is the optimal conditions. The degradation efficiencies are higher than 99 % in all cases. The effect of different solvents was also studied and analyzed by GC-MS. DD has great degradation efficiency by using hexane as the reaction solvent. However, 2CDD and DBF have the same degradation products by using hexane or methanol. 4-BDPE will degrade into small molecules by using mixed solvent or methanol. Various templates for embedding the palladium metal was also studied by replacing graphene with carbon nanofiber to prepare a palladium/carbon nanofiber composite catalyst (Pd/CNF). The experimental results show that Pd/CNF has similar degradation capability to DD, 2CDD, DBF, and 4-BDPE as compared to Pd/G. Simulated real sample study was done by spiking 2CDD into lard and performing degradation of the 2CDD in situ. The results show that 2CDD can be fully degraded by the Pd/G catalyst.
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Liao, Chen-yuan, et 廖振淵. « Degradation of Dioxin in Fly Ashes via Pyrolysis ». Thesis, 2010. http://ndltd.ncl.edu.tw/handle/64440340148960078514.
Texte intégralRésumé :
碩士國立中央大學
環境工程研究所
98
The major fly ash sources in Taiwan include municipal solid waste incinerators (MSWIs), electric arc furnaces (EAFs) and secondary metal smelting processes. Because fly ashes contain high concentration of dioxin and heavy metal, they belong to hazardous waste and have to be treated before its releases. Fly ashes account for 62% of total hazardous industrial waste in Taiwan, and fly ashes are mostly treated with stabilization/solidification in Taiwan, resulting in the increase of fly ash volume. So how to efficiently lower the toxicity in fly ashes, reducing the stabilization/solidification fly ashes volume are the most important issue in Taiwan. This study is motivated to understand the fly ash characteristics and construct a pyrolysis system for degrading dioxins in the fly ashes. The fly ashes investigated in this study include municipal solid waste incinerators fly ashes, electric arc furnaces fly ashes, Waelz process fly ashes and secondary copper smelting fly ashes. The results show that the dioxin removal efficiency is higher as the reaction time gets longer or temperature gets higher. At 3 hour, 400oC, 100% nitrogen flow, the dioxin removal efficiency is 98.1% in MWI fly ashes, 26% in secondary copper smelting fly ashes, 72% in EAF fly ashes; it shows that MWI fly ash has the highest dioxin removal efficiency. The dioxin removal efficiencies do not change significantly whether the system contains the flow or not. Dioxin formation is observed when the flow contains 5% oxygen, and the secondary copper smelting fly ashes is of the highest formation. The dioxin removal efficiency achieved by adding Ca(OH)2 is higher than that of adding CaO.
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Shi, Tjaun-En, et 謝宗恩. « Photocatalytic degradation of nitrobenzene using titanium dioxide ». Thesis, 2006. http://ndltd.ncl.edu.tw/handle/09590258466631230201.
Texte intégralRésumé :
碩士國立成功大學
化學系碩博士班
94
It is an important challenge to search a powerful and efficient pathway to degrade adverse chemicals or waste water. In this study we used immobilization powdered titanium dioxide coated on a cylindrical quartz tube to degrade nitrobenzene and alter the environmental condition in a simulated system. Variations of nitrobenzene concentration, pH value, temperature, and dissolving oxygen were studied. Two types of commercial titanium dioxides, Degussa P-25 and Hombikat UV-100, were compared each other in the degradation efficiency of nitrobenzene. It is shown that two commercial titanium dioxides have the same reaction rate constant of pH in the order of 7 > 4 > 11 in a 3-hour degradation of 0.407 mM nitrobenzene in the origin. Moreover, Degussa P-25 has the best photodegradation efficiency in the solution of pH = 7. For the study of concentration variation, the adsorption coefficient Kad and the reaction rate constant kLH were obtained to be 0.024 L/mg and 0.024 mg/L.min, respectively, with the concentration of nitrobenzene in 0.407, 0.813, 1.220, 1.626, and 2.439 mM. In the temperature variation study, the reaction activation energy Ea, the enthalpy of activation DH┿, and the entropy of activation DS┿ were obtained to be 34.45 kJ/mol, =0.31 kJ/mol, and =-0.041 J/K.mol, respectively, with the concentration 0.407 mM of nitrobenzene under different temperatures of 20, 30, and 40oC. We also tested the influence of the aeration in the reactor. It is shown that the greater degradation the more amount of air flow rate. In the largest amount of air flow rate of 150 mL/min used in the study, oxygen dissolved in the solution was detected to be 7.2 ± 0.3 mg/L. The reaction rate constant k was obtained to be 1.28 x 10-2 ± 0.05 min-1 in a 3-hour reaction for the residual of 8 %. In the reaction condition of followings, 1.626 mM of nitrobenzene, pH=7, 30 oC, 150 mL/min of air flow rate for a 10-hour reaction, we identified some intermediates of 2-nitrophenol, 3-nitrophenol, 4-nitrophenol, and some other unknown chemical compounds by means of HPLC and GCMS instrumentation.
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Luck, Anni. « UV/titanium dioxide for drinking water treatment : Concurrent degradation of 1,4-dioxane and removal of iron and manganese ». 2007. http://link.library.utoronto.ca/eir/EIRdetail.cfm?Resources__ID=452983&T=F.
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cheng, Lou wei, et 羅偉誠. « Modifying titanium dioxide photocatalyst to fulfill the degradation Modifying titanium dioxide photocatalyst to fulfill the degradation Modifying titanium dioxide photocatalyst to fulfill the degradation of salicylic acid under visible-light ». Thesis, 2010. http://ndltd.ncl.edu.tw/handle/25097179523506886839.
Texte intégralRésumé :
碩士國立暨南國際大學
土木工程學系
98
This study using metal (Fe、Ni) modified TiO2 catalysts nano-photocatalysts were prepared by sol-gel process. This modification results in catalysts with enhanced visible light absorbance in blue light region . The Fe-TiO2 were 0、0.01、0.05、0.1、0.5 wt% respectively. The Ni-TiO2 were 1、5、10、15 wt% respectively.. The calcined at 400℃、500℃、600℃、700℃. Degradation of salicylic acid respectively under three kind of light sources the visible light lamp (400-500 nm), solar light, the daylight lamp. These catalysts were characterized by the use of Brunauer-Emmett-Teller (BET)、X-ray diffraction (XRD )and Field emission Scanning Electron Microscope (FESEM). The BET surface area test of the catalysts was 90.12 ~103.44 m2/g. The XRD results, the pure and modified TiO2 calcined at 500 ◦C Began to have a small amount of Rutile phase appears at 700 ◦C are in anatase form. Modification of metals did not cause phase transformation. The Photocatalysis Degradation of salicylic acid test received the following results. Using Ferrum to modify TiO2, the Fe-TiO2 (0.1 wt%) had the greatest photocatalytic activity. Similarly, using Nickel to modify TiO2, the Ni-TiO2 (10 wt%) had the greatest photocatalytic activity. At the best ratio of modified, preparing TiO2 in different sintered temperatures received the TiO2 which had higher photocatalytic activity at the temperature of 400 ℃. Degrade salicylic acid under the three kinds of light sources including visible light, fluorescent light, and solar light. The degradation has the best photocatalytic activity when the solar light as the light source. In the study, informed that the degradation of salicylic acid is first-order linear regression.
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Chin, Paul. « Kinetics of photocatalytic degradation using titanium dioxide films ». 2008. http://www.lib.ncsu.edu/theses/available/etd-04032008-121402/unrestricted/etd.pdf.
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Freeman, Stephanie Anne. « Thermal degradation and oxidation of aqueous piperazine for carbon dioxide capture ». Thesis, 2011. http://hdl.handle.net/2152/ETD-UT-2011-05-3290.
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Absorption-stripping with aqueous, concentrated piperazine (PZ) is a viable retrofit technology for post-combustion CO2 capture from coal-fired power plants. The rate of thermal degradation and oxidation of PZ was investigated over a range of temperature, CO2 loading, and PZ concentration. At 135 to 175 °C, degradation is first order in PZ with an activation energy of 183.5 kJ/mole. At 150 °C, the first order rate constant, k1, for thermal degradation of 8 m PZ with 0.3 mol CO2/mol alkalinity is 6.12 × 10-9 s-1. After 20 weeks of degradation at 165 °C, 74% and 63%, respectively, of the nitrogen and carbon lost in the form of PZ and CO2 was recovered in quantifiable degradation products. N-formylpiperazine, ammonium, and N-(2-aminoethyl) piperazine account for 57% and 45% of nitrogen and carbon lost, respectively. Thermal degradation of PZ likely proceeds through SN2 substitution reactions. In the suspected first step of the mechanism, 1-[2-[(2-aminoethyl) amino]ethyl] PZ is formed from a ring opening SN2 reaction of PZ with H+PZ. Formate was found to be generated during thermal degradation from CO2 or CO2-containing molecules.
An analysis of k1 values was applied to a variety of amines screened for thermal stability in order to predict a maximum recommended stripper temperature. Morpholine, piperidine, PZ, and PZ derivatives were found to be the most stable with an allowable stripper temperature above 160 °C. Long-chain alkyl amines or alkanolamines such as N-(2-hydroxyethyl)ethylenediamine and diethanolamine were found to be the most unstable with an allowable stripper temperature below 120 °C.
Iron (Fe2+) and stainless steel metals (Fe2+, Ni2+, and Cr3+) were found to be only weak catalysts for oxidation of PZ, while oxidation was rapidly catalyzed by copper (Cu2+). In a system with Fe2+ or SSM, 5 kPa O2 in the inlet flue gas, a 55 °C absorber, and one-third residence time with O2, the maximum loss rate of PZ is expected to 0.23 mol PZ/kg solvent in one year of operation. Under the same conditions but with Cu2+ present, the loss rate of PZ is predicted to be 1.23 mole PZ/kg solvent in one year of operation. Inhibitor A was found to be effective at decreasing PZ loss catalyzed by Cu2+. Ethylenediamine, carboxylate ions, and amides were the only identified oxidation products. Total organic carbon analysis and overall mass balances indicate a large concentration of unidentified oxidation products.text
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Wei-TengHung et 洪偉騰. « The study of microbial degradation for dioxin in soil and sludge ». Thesis, 2018. http://ndltd.ncl.edu.tw/handle/d4bkbq.
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Liao, Guan-Lin, et 廖冠琳. « The degradation of PCBs using zinc and titanium dioxide composite with silicon dioxide photocatalyst ». Thesis, 2015. http://ndltd.ncl.edu.tw/handle/31844926505198669555.
Texte intégralRésumé :
碩士國立屏東科技大學
環境工程與科學系所
103
Photodegradation is one of the most important mechanisms of natural degradation for organic pollutants in environment especially through the indirect photodegradation. The advantage of indirect photodegradation can be an efficient method with low equipment cost, less complicated operation processes, low energy consumption, and capable of using solar energy. Polychlorinated biphenyls (PCBs) have been widely used in industries. PCBs are highly stable man-made organic matters. However, PCBs are not easily biodegradable, a group of persistent organic pollutants. When PCBs released to the environment through the transportation of atmosphere, water, organisms and soil in the various environmental media they can be accumulated in organisms because of the contamination in the environment. Titanium dioxide (TiO2) and Zinc (Zn) have low cost and non-toxic properties. After Zn particles embedded TiO2 the charge separation producing an electron-hole pairs under the exposure of the lights. TiO2 has a high performance light catalytic ability. The silicon dioxide (SiO2) can improve TiO2 thermal stability. The sol-gel preparation of Zn and TiO2 composite with SiO2 with defferent amounts of Zn are used to form pure TiO2, pure SiO2, TiO2-SiO2, TiO2- SiO2/ Zn (0.5、0.7、1.0 wt％) and different binding order of Zn-SiO2/TiO2 (0.5、0.7、1.0 wt％). Zn was applied to enhance the photocatalytic capacity to improve the visible light absorption and to further explore the treatments of methylene blue and PCBs aqueous solutions. The results found that the catalyst complex can accelerate the degradation efficiency of pollutants under natural sunlight. The findings of FE-SEM tests showed that the doping of Zn did not affect its surface. The XRD analytical results were used to compare the JCPDS authentication database used in this study. The main dominant species comfirmed the catalyst types with all highly photocatalytic activity of TiO2. Degradation percentages of methylene blue were 100 % under natural sunlight after 2 hours exposure except for the sample of Pure TiO2 and Pure SiO2. The degradation percentages of PCBs were up to 43.52% and 15.55% of mineralization. PCBs concentration decreased with increasing illumination times. The results indicated that 0.7 and 1.0 wt% Zn-SiO2/TiO2 calcined at 600℃ by sol-gel method can be reused, and it confirmed their economical benefits of environmental protection techniques.
45
Nadupalli, Srinivasu. « Oxidative degradation of textile dyes with hypochlorite and chlorine dioxide ». Thesis, 2010. http://hdl.handle.net/10413/5359.
Texte intégralRésumé :
The oxidation reaction mechanisms of water soluble textile dyes amaranth (an azo dye), brilliant
blue-R (a triaryl dye) and safranine-O (an azine dye) with oxidants- hypochlorite and chlorine
dioxide, were investigated. The detailed kinetics of the reactions of the three dyes was studied
under excess concentrations of the oxidant and other reagents. The depletion of concentration of
the chosen dye, taken at low concentration was monitored using a Hi-Tech SF-61 DX2 double
mixing micro volume stopped-flow apparatus.
The hypochlorite initiated oxidations were investigated as function of varying concentration of
oxidant and hydrogen ion, ionic strength and temperature. For the chosen dyes and reaction
conditions, the depletion of dye followed pseudo first-order kinetics and the rate constants were
estimated using KinetAsystTM software. All the three reactions had first-order dependence on the
oxidant concentration, and the reaction rates increased by varied extent with increase in [H+]0.
The role of acid in their reaction mechanisms was established. The kinetic data was analysed to
evaluate the rate constants for the competitive pathways initiated by hypochlorite ion and
hypochlorous acid. The overall second-order rate coefficients for the OCl- and HOCl initiated
reactions were estimated for all the three reactions. Major oxidation products for the reactions
were separated and characterized by 1H NMR and 13C NMR and GC-MS techniques and the
stoichiometry was established. The energy parameters inclusive of Arrhenius factor, enthalpy,
entropy and energy of activations for the oxidation of three dyes both by OCl- and HOCl species
were estimated. Based on the experimental findings, the probable rate laws, mechanisms and
reaction schemes were described. Simulations studies were conducted to validate the proposed
mechanisms using SIMKINE2 computer programme. The rate of oxidation of safranine-O is
greater than that of amaranth and brilliant blue-R with OCl- / HOCl reaction.
Following similar protocol, the oxidations of the chosen dyes with chlorine dioxide were
investigated by monitoring the depletion kinetics of dye as function of varying concentration of
ClO2 and OH- ion, ionic strength and temperature. All the three dyes, exhibited pseudo first-order
kinetics and the rate constants were estimated using KinetAsystTM software. All the three
reactions had first-order dependence on the oxidant concentration at pH conditions 7.0, 8.0 and
9.0 suggesting that reaction mechanism remains unaltered with pH variation. The effect of
hydroxide ion on the reaction rate revealed that it acts as catalyst. All the three reactions had
first-order dependence on [OH-]0, when its concentration was low; but the order with respect to
[OH-] decreased as [OH-] increased stoichiometry proportion to reactants. The catalytic constant
for hydroxide catalysed reaction was estimated for all the three reactions. Kinetic salt effect
experiments were conducted to identify the possible reaction species involved in the reactions.
The major reaction products were characterized by 1H NMR, 13C NMR and GC-MS techniques.
The stoichiometry ratios were established and energy parameters were estimated. The rate laws
and probable reaction mechanisms were proposed and appropriate reaction schemes for all the
reactions were described. The elucidated mechanisms were confirmed by simulation studies
using SIMKINE2 software. At neutral pH the rate of oxidation of amaranth is greater than
safranine-O and brilliant blue-R, and brilliant blue R being the slowest.Thesis (Ph.D.)-University of KwaZulu-Natal, Westville, 2010.
46
Davis, Jason Daniel. « Thermal degradation of aqueous amines used for carbon dioxide capture ». 2009. http://hdl.handle.net/2152/6581.
Texte intégralRésumé :
Aqueous amine solutions loaded with CO2 were degraded in stainless steel sealed containers in forced convection ovens. Amine loss and degradation products were measured as a function of time by cation chromatography (IC), HPLC, and IC/mass spectrometry. A full kinetic model was developed for 15-40 wt% MEA (monoethanolamine) with 0.2 – 0.5 mol CO2/mol MEA at 100°C to 150°C. Experiments using amines blended with MEA demonstrate that oxazolidone formation is the rate-limiting step in the carbamate polymerization pathway. With 30 wt% MEA at 0.4 mol CO2/mol MEA and 120°C for 16 weeks there is a 29% loss of MEA with 13% as hydroxyethylimidazolidone (HEIA), 9% as hydroxyethylethylenediamine (HEEDA), 4% as the cyclic urea of the MEA trimer, 1-[2-[(2-hydroxyethyl)amino]ethyl]-2-imidazolidone, 3% as the MEA trimer, 1-(2-hydroxyethyl)diethylenetriamine, and less than 1% as larger polymeric products. In the isothermal experiments, thermal degradation was slightly more than first order with amine concentration and first order with CO2 concentration with an activation energy of 33 kcal/mol. In a modeled isobaric system, the amount of thermal degradation increased with stripper pressure, but decreased with an increase in amine concentration and CO2 concentration due to a reduction in reboiler temperature from the changing partial pressure of CO2. Three-fourths of thermal degradation in the stripper occurred in the reboiler due to the elevated temperature and long residence time which offset the decrease in CO2 concentration compared to the packing. The amount of degradation for other amines tested starting with the least degraded include; cyclic amines with no side chains < long chain alkanolamines < alkanolamines with steric hindrance < tertiary amines < MEA < straight chain di- and triamines. Piperazine and morpholine had no measurable thermal degradation under the conditions of this experiment and were the most resistant to thermal degradation. Diethyelenetriamine and HEEDA had the largest amount of degradation with over 90% loss at 135°C for 8 weeks.text
47
Tien, Chao-Cheng, et 田照正. « Photoelectrocatalytic Degradation of Dyes using Graphene Composite Titanium Dioxide Electrodes ». Thesis, 2014. http://ndltd.ncl.edu.tw/handle/23723560957186331834.
Texte intégralRésumé :
碩士朝陽科技大學
環境工程與管理系
102
The ultrasonic and Hummers method were used in this study to prepare graphene oxide. The cyclic voltammetry was used for reduction of graphene oxide to graphene and deposition of graphene on the TiO2 nanotube array film. Thus, the graphene composited TiO2 nanotube array film was prepared. The photoelectrocatalysis of dye solution and its degradation efficiency was implemented with visible light and UV. The open-circuit voltage, closed circuit current and AC impedance of electrochemical analysis were implemented. The results showed that the dye degradation efficiency of the graphene composite TiO2 nanotube array film in UV-irradiation is better than that of TiO2 nanotube array film. With bias of 1 V, the addition of 0.1 M potassium chloride resulted in the optimum photoelectrocatalytic degradation efficiency. The degradation efficiency is still good when the methyl orange solution concentration is increased to 30 mg/L. The photocurrent of graphene composite TiO2 nanotube array film was increased compared with TiO2 nanotube array film. The results proving that the graphene composite TiO2 nanotube array film can increase the overall photoelectrocatalytic efficiency. In the same way, photocatalysis and photoelectrocatalysis of methyl orange solution with the visible light showed that the graphene composite TiO2 nanotube array film also has better catalytic efficiency than TiO2 nanotube array film.
48
« Gaseous phase photocatalytic degradation of volatile organic compounds by titanium dioxide ». 1999. http://library.cuhk.edu.hk/record=b5890093.
Texte intégralRésumé :
by Yuk-Lin Chan.Thesis (M.Phil.)--Chinese University of Hong Kong, 1999.
Includes bibliographical references (leaves 78-83).
Abstracts in English and Chinese.
Abstract (English version) --- p.i
Abstract (Chinese version) --- p.ii
Acknowledgments --- p.iii
Table of Contents --- p.iv
List of Figures --- p.vi
List of Tables --- p.vii
Chapter 1. --- Introduction
Chapter 1.1 --- Indoor Air Pollution --- p.1
Chapter 1.2 --- Typical Treatment of Air Pollutant --- p.6
Chapter 1.3 --- Photocatalytic Degradation over Titanium Dioxide --- p.7
Chapter 1.4 --- Advantages of Titanium Dioxide as a Photocatalyst --- p.12
Chapter 1.5 --- Applications of Photocatalytic Degradation in Pollution Control --- p.14
Chapter 1.5.1 --- Aqueous Phase Decontamination --- p.15
Chapter 1.5.2 --- Gas Phase Decontamination --- p.15
Chapter 1.6 --- Development of the Photocatalytic Degradation Technique --- p.16
Chapter 1.6.1 --- Pure Ti02 --- p.17
Chapter 1.6.2 --- Design of the Reactors --- p.18
Chapter 1.6.3 --- Metal Ion Dopants --- p.21
Chapter 1.6.4 --- Mixture with Supports --- p.21
Chapter 1.7 --- Adsorbent-Supported Titanium Dioxide --- p.22
Chapter 1.7.1 --- Use of Adsorbents other than Zeolites --- p.22
Chapter 1.7.2 --- Use of Zeolites --- p.25
Chapter 1.8 --- Molecular Sieves --- p.29
Chapter 2. --- Experimental
Chapter 2.1 --- Block diagram of the Reaction Setup --- p.31
Chapter 2.2 --- Fixed Volume Batch Reactor --- p.32
Chapter 2.3 --- Reagents --- p.34
Chapter 2.3.1 --- Degussa P25 Ti02 powder --- p.34
Chapter 2.3.2 --- Aldrich Molecular Sieves (Organophilic) --- p.35
Chapter 2.3.3 --- Other Adsorbents Used for Comparison --- p.35
Chapter 2.4 --- Instrumental Analysis --- p.36
Chapter 2.4.1 --- Photoacoustic Multi-gas Monitor --- p.36
Chapter 2.4.2 --- X-Ray Diffraction Analysis --- p.42
Chapter 2.4.3 --- Scanning Electron Microscopy --- p.42
Chapter 2.4.4 --- UV-vis Diffuse Reflectance Spectroscopy --- p.42
Chapter 2.4.5 --- Iso-electron Point Measurements --- p.43
Chapter 2.5 --- Photocatalytic Degradation of Simple Alkanes by P25 Titanium Dioxide --- p.45
Chapter 2.6 --- Photocatalytic Degradation of Gaseous Acetone over Organophilic Molecular Sieves-Supported Titanium Dioxide --- p.49
Chapter 3. --- Results and Discussion
Chapter 3.1 --- Photocatalytic Degradation of Simple Alkanes by P25 Titanium Dioxide --- p.52
Chapter 3.1.1 --- Rate of Photocatalytic Degradation of Simple Alkanes --- p.52
Chapter 3.1.2 --- Summary of Rate of Photocatalytic Degradation of Simple Alkanes --- p.57
Chapter 3.2 --- Photocatalytic Degradation of Gaseous Acetone over Organophilic Molecular Sieves-Supported Titanium Dioxide --- p.58
Chapter 3.2.1 --- The Adsorption Ability of Various Adsorbents --- p.58
Chapter 3.2.2 --- XRD Pattern Measurement --- p.60
Chapter 3.2.3 --- Scanning Electron Microscopy --- p.64
Chapter 3.2.4 --- UV-vis Diffuse Reflectance Spectroscopy --- p.65
Chapter 3.2.5 --- Iso-electron Point Measurements --- p.67
Chapter 3.2.6 --- Photocatalytic Activity of Various Catalysts --- p.69
Chapter 4. --- Conclusion --- p.76
Bibliography --- p.78
Appendix
"A Demonstration of Photocatalytic Degradation by Gaseous Organic Pollutant, Dichloromethane " --- p.83
49
Liou, Chyuan-Der, et 劉全得. « The Characteristics of Photocatalytic Degradation of Azo Dyes by Titanium Dioxide ». Thesis, 2005. http://ndltd.ncl.edu.tw/handle/87657346737643663326.
Texte intégralRésumé :
碩士國立高雄第一科技大學
環境與安全衛生工程所
93
The residual color is one of the major pollutants in dyeing wastewater and is difficult to remove by traditional bio-treatment units. The research aims on investigating the degradation of azo dyes via UV/TiO2 photocatalytic Oxidation processes. In the study, anatase TiO2 was applied as the photocatalyst and a near-UV light with main emission wavelength around 360 nm was used as the light source. Three in-using azo dyes including single-azo(Orange GGC), di-azo(Yellow G) and tri-azo(Brown NR) dyes were examined in the investigation. Several experimental parameters including solution pH levels, light intensity (71-236 �巰/cm2), photocatalyst dosage (500-4000mg/L) and chlorine salt concentration (0-30000mg/L) were investigated in the research. Experimental results demonstrated that high concentration TiO2 and illuminated light intensity could enhance the degradation rates of azo dyes. But the concentration of TiO2 could not be too high to prevent interfere illuminated light intensity. For the effect of solution pH on the reaction rates, faster degradation reaction rates were usually detected in neutral or acidic environment. For the effect of chloride concentration on the degradation rates, the degradation rates of the dyes decreased with chloride concentration. In addition, it was observed that the degradation reaction rates of the dyes decreased with chloride concentration. An empirical formula was developed to establish the relationships among the pseudo-first-order reaction rate constant and the tested operation conditions. The experimental results also demonstrated that more than 90 % of residual color can be reduced in short reaction period when suitable operation conditions were applied.
50
Chen, Hsiang-Yu, et 陳香羽. « Removal and Degradation of Persistent Organic Pollutants by Supercritical Carbon Dioxide ». Thesis, 2012. http://ndltd.ncl.edu.tw/handle/58477713494510138654.
Texte intégralRésumé :
博士中原大學
化學研究所
100
Persistent organic pollutants (POPs) are organic pollutants that are resistant to degradation which possess four characteristics：persistence, semi-volatility, bio-accumulativeness, and high toxicity. Since POPs have great impacts on the environment and human health, the removal of these contaminants and/or their degradation present an important task for the researchers. In the first part of this study, a simple method that employs concentrated HNO3 as a suppression agent and methanol-modified supercritical carbon dioxide (Sc-CO2) extraction is proposed for the removal of PFOS and PFOA from solid matrices. The optimal conditions were found to be 16 M HNO3 and Sc-CO2 containing 20% (v/v) methanol under 200 atm pressure at 50 °C, with 70 min extraction time (40 min for static and 30 min for dynamic extraction). PFOA and PFOS were identified and quantified by high performance liquid chromatography/mass spectrometry (HPLC/MS). The extraction efficiencies (with double extractions) are near 100% for PFOA and 80% for PFOS for both paper and fabric matrices. The results show that this method is quick, convenient, accurate, and effective, providing a promising and convenient approach to remediate the environment from the contamination of hazardous PFOA and PFOS. In the second part, a method for the degradation of dioxins and polybrominated biphenyls (PBBs) catalyzed by palladium nanoparticles stabilized in microcellular high-density polyethylene (Pd/m-HDPE) in supercritical carbon dioxide is described. Preparation of Pd/m-HDPE is divided into three steps; foaming in supercritical fluid, impregnation in supercritical fluid, and reduction by hydrogen. Dioxins and PBBs can be effectively degraded under 200 atm of CO2 containing 10 atm of H2 at 50-100℃ using the Pd/m-HDPE catalyst. Stepwise removal of chlorine/bromine atoms takes place first, followed by hydrogenation of the two benzene rings with slower reaction rates. The Pd/m-HDPE catalyst is easy to prepare and can be reused without losing its activity even after 50 times. This heterogeneous catalyst is eco-friendly and can be easily separated from the products without complicated recovery and cleaning procedures.